CN112285320A - Human health risk assessment method for heavy metal contaminated soil - Google Patents
Human health risk assessment method for heavy metal contaminated soil Download PDFInfo
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Abstract
The invention discloses a method for evaluating human health risks of heavy metal contaminated soil, which comprises the following steps: firstly, respectively constructing functional relations C1(pH) and C2(pH) among leaching concentration, acid dissolved state concentration and pH value of a leaching agent of heavy metal in a soil sample; then, the human health risk concentration C in the soil sample is calculatedrisk: wherein, Crisk0.5 xc 1(pH) +0.5 xc 2 (pH); then, calculating the total carcinogenic risk and/or hazard index of the heavy metals in the soil sample by referring to relevant parameters and calculation models provided in technical guidelines for evaluating the risk of soil pollution of construction sites (HJ 25.3-2019); and finally, evaluating whether the heavy metal contaminated soil has human health risks or not by referring to the (HJ25.3-2019) evaluation standard. The method is more strict, and dynamic assessment of human health risks of the heavy metal contaminated soil which is recycled after being repaired under different pH environmental conditions is realized.
Description
Technical Field
The invention belongs to the field of soil pollution risk control and human health risk evaluation, and particularly relates to a human health risk assessment method for heavy metal polluted soil.
Background
With the acceleration of urbanization process and transformation of industrial structure in China, urban land resources are more scarce due to the fact that a large number of people embrace cities, land cost is continuously increased, and a large number of industrial enterprises originally located in the central areas of the cities are forced to be transferred to suburbs of the cities. The adjustment of the industrial structure directly causes the conventional backward capacity enterprises and old factories to face the shut-down or relocation situation. According to incomplete statistics, more than 10 thousands of enterprises in China need to be shut down or moved in recent years, and more than 2000 polluted enterprises which have been or are to be moved in recent years in the Yangtze delta region only. The enterprises are mostly engaged in the industries of electroplating, printing and dyeing, chemical fertilizers, pesticides and the like, and a large amount of heavy metals enter soil due to old equipment of the enterprises, discharge of three industrial wastes, running, overflowing, dripping, leaking and the like in the production process, so that the original industrial enterprise site becomes a high-risk area polluted by the heavy metals. More seriously, because the population density of China is high and the urban land resources are in short supply, the polluted sites can be rapidly re-developed and utilized to build new plants, residential areas, commercial areas and the like. If the heavy metal polluted sites cannot be effectively managed and risk evaluated, the heavy metal polluted sites become a 'chemical timed bomb', which threatens the ecological environment safety of a recycling area and brings serious influence on subsequent development and construction.
The heavy metal contaminated soil can be reused after being repaired. The current common heavy metal contaminated soil remediation method mainly comprises the following steps: physical repair techniques, chemical repair techniques, phytoremediation techniques, and the like. The physical remediation technology comprises the treatment of washing, digging, transporting, landfill and the like aiming at the heavy metal contaminated soil, can thoroughly remove the metal pollutants in the field, but has high treatment cost and limited landfill field number due to the potential secondary pollution, and is difficult to be applied on a large scale; the chemical remediation technology is mainly an in-situ solidification/stabilization method of heavy metals, and the form or structure of the heavy metals is changed by applying a stabilization/solidification treatment material, so that the purpose of reducing the mobility of the heavy metals is achieved, and the method is also the most widely applied remediation technology of the heavy metal contaminated soil at present; plant restoration, as a green restoration technology, can prevent the destruction of the landscape of the earth surface to a great extent and protect the original appearance of the soil, but the application of the technology is also limited by low efficiency, long restoration time and vulnerability of the plants to specific climatic conditions, and is difficult to popularize in a large range. Therefore, the chemical remediation method of heavy metal contaminated soil by a curing/stabilizing method is still the most efficient and practical method at present, and in the in-situ stabilizing/curing method of heavy metals, the high-temperature curing treatment technology is widely and practically applied due to high curing rate of the heavy metals and stable and reliable effect. High temperature solidification technology mainly by high temperature sinteringThe method comprises the steps of fully mixing and reacting heavy metal contaminated soil with auxiliary reaction materials such as coal gangue, fly ash and shale, forming a spinel structure after sintering, and firmly fixing heavy metals in the stable spinel structure. Spinel is commonly denoted "AB2O4", wherein A represents, for example, Zn2+、Cu2+、Cd2+And Ni2+Divalent heavy metals, B being e.g. Cr3+And Al3+And the like. Spinel has good structural stability, and can stably consolidate polluted heavy metal ions in a sintered body for a long time without generating secondary pollution even under the conditions of strong acid and strong alkali, so the spinel is widely considered as a promising method for repairing heavy metal polluted soil.
Soil is an important component of the ecosystem and is also the material foundation on which humans rely for survival. The recycling of the heavy metal contaminated soil after remediation is an effective means for relieving the serious shortage of soil resources in China. However, since the high-temperature curing technology is not a heavy metal pollution reduction technology in general, the total amount of heavy metals in the soil after remediation is not reduced per se. The core mechanism of the method is to stabilize the heavy metal through the change of the heavy metal morphological structure, reduce the possibility of releasing the heavy metal into the environment, and is a risk control technology. Therefore, after the heavy metal contaminated soil is repaired by the high-temperature curing technology, the long-term stability of the heavy metal and the possible human health risks directly influence the acceptance and application range of the technology, and are also the problems which need to be considered when the repaired soil is reused. As a typical soil heavy metal pollution risk control technology, the high-temperature curing technology changes the occurrence form of heavy metals in soil, thereby achieving the purpose of reducing the migration and bioavailability of the heavy metals. However, since the polluted heavy metals are not completely eliminated, there still exists a certain question and risk if the heavy metals in the soil repaired by high-temperature curing are further released under the complicated practical application environmental conditions in the future, and a corresponding quantitative evaluation method is also very lacking.
For a long time, the benefit-related parties in the process of repairing the heavy metal contaminated soil mainly pay attention to the effect evaluation of the soil contamination repairing technology, and the concern on the recycling direction of the repaired soil and the possible human health risks generated in the recycling process under different environmental conditions is less. Currently, commonly used human health Risk assessment methods for heavy metal contaminated soil mainly include the Standard Guide for Risk-Based Corrective Action, ASTM E-2081 in the United states, the CLEA Model Technical Background update document (Updated Technical Background to the CLEA Model) in the United kingdom, and the Technical Guide for Risk assessment of soil contamination in construction sites (HJ25.3-2019) which is the latest in China (Technical guides for Risk assessment of soil contamination for land use) and the like. The human health risk evaluation models quantitatively calculate the potential human health risk of the polluted soil mainly according to carcinogenic and non-carcinogenic effects which can be generated after the human body is contacted with the heavy metal pollutants under various exposure ways. And for the repaired soil, the content of the potential heavy metals which can be released under the complex environmental conditions is the key for evaluating the human health risk. The most common methods for accurately analyzing the content of heavy metals released by the repaired soil are toxic leaching methods, including a TCLP toxic leaching method for simulating landfill leachate, an SPLP leaching method for simulating acid rain leaching, an MEP multi-stage leaching method for simulating multiple acid rain erosion of a landfill and the like, which are provided by the United States Environmental Protection Agency (USEPA). The solid waste leaching toxicity leaching method proposed by the department of ecological environment in China comprises a horizontal oscillation method (HJ557-2010), a sulfuric acid-nitric acid method (HJ/T299-2007), an acetic acid method (HJ/T300-2007) and the like. The method takes the leaching content of the heavy metal of the repaired soil under a certain specific pH condition (usually a strong acid condition) and within a specific reaction time period as an evaluation standard, and does not consider the influence of the morphological change characteristics of the heavy metal on the release of the heavy metal in the repaired soil. The commonly used leaching toxicity evaluation methods are mainly applied to evaluation of the remediation effect of the heavy metal contaminated soil, but due to the limitations of the methods, the methods cannot completely simulate different situations of pollutant release to the environment after remediation in practice, and the long-term human health risk in the complex and variable environment is difficult to characterize. Particularly, different recycling environments have complicated and variable pH conditions, and different pH conditions directly influence the release amount of heavy metals in the repaired soil, so that the generated human health risks are greatly different. If, for example, under acidic conditions, most heavy metals (Zn, Cu, Pb, etc.) exhibit stronger release characteristics compared to alkaline conditions, it is clear that the actual human health risks under application scenarios of neutral and alkaline environments are significantly overestimated if all application scenarios of the repaired soil are evaluated using only traditional solid waste leaching toxicity leaching methods, such as the nitric sulfate method (HJ/T299-2007) and the acetic acid method (HJ/T300-2007). Meanwhile, the high-temperature curing repair process of the heavy metal contaminated soil is accompanied by the change of the morphological structure of the heavy metal, the acid soluble state in the soil is the highest in bioavailability and the most harmful to the environment, and the acid soluble state heavy metal in the contaminated soil can be effectively converted into the reduction state, oxidation state and residue state heavy metal with higher stability through the high-temperature curing technology, so that the aim of effectively reducing the human health risk of the heavy metal contaminated soil is fulfilled. However, the traditional toxic leaching method usually ignores the aspect of the morphological change of the heavy metal, so that the human health risk of the soil under the neutral or alkaline condition after high-temperature curing and repairing is underestimated, the human health risk of the soil under the neutral or alkaline condition without high-temperature curing and repairing is overestimated, and the uncertainty of the evaluation of the human health risk of the soil after repairing is increased. The current prospect of safe recycling of the restored soil is directly influenced by the lack of a human health risk assessment system of the restored soil, and the actual risk possibly generated by the restored soil under the complex pH conditions of different recycling situations can be more scientifically and reasonably evaluated by considering the leaching concentration and the acid dissolution state concentration of the restored soil at the same time. Therefore, the development of a suitable human health risk assessment method aiming at the recycling of heavy metal contaminated soil after remediation is urgently needed.
Disclosure of Invention
In order to overcome the defects of the existing heavy metal contaminated soil human health risk assessment method, the invention aims to provide a heavy metal contaminated soil human health risk assessment method.
The second aspect of the invention aims to provide application of the method for assessing the human health risk of the heavy metal contaminated soil in the field of environmental monitoring.
Interpretation of terms in the present invention:
carcinogenic risk: the probability of exposure of a human population to a carcinogenic pollutant to induce a carcinogenic disease or injury is used to characterize the level of harm done to the human body by a single route of exposure to a carcinogenic pollutant.
Total carcinogenic risk: the sum of the carcinogenic risks of a population exposed to a single pollutant via multiple pathways is used to characterize the level of harm to the human body from exposure to the carcinogenic pollutant.
Hazard quotient: the ratio of the daily intake dose of a contaminant to a reference dose is used to characterize the level of harm that a human is exposed to a non-carcinogenic contaminant via a single route.
Hazard index: the sum of hazard quotients of a population exposed to a single pollutant via multiple routes is used to characterize the level of harm to a human exposed to a non-carcinogenic pollutant.
Acceptable risk level: risk levels that do not produce adverse or unhealthy effects in the exposed population include acceptable total carcinogenic risk levels for carcinogens and acceptable hazard indices for non-carcinogens. The acceptable total carcinogenic risk level for a single pollutant in this standard is 10-6The acceptable hazard index for a single contaminant is 1.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the invention provides a method for evaluating human health risks of heavy metal contaminated soil, which comprises the following steps:
(1) respectively leaching heavy metals in the soil sample in leaching agents with different pH values, and measuring the leaching concentration C1 of the heavy metals in the soil sample under the leaching agents with different pH values to obtain a functional relation C1(pH) between the leaching concentration of the heavy metals in the soil sample and the pH value of the leaching agent;
(2) measuring the acid soluble state concentration C2 of the heavy metal in the soil sample leached in the step (1), and constructing a functional relation C2(pH) between the acid soluble state concentration of the heavy metal in the soil sample and the pH value of the leaching agent;
(3) calculating human health risk concentration C in soil samplerisk: wherein, Crisk＝0.5×C1(pH)+0.5×C2(pH)；
(4) Calculating the total carcinogenic risk and/or hazard index of the heavy metals in the soil sample;
(5) and evaluating whether the human health risk of the heavy metal contaminated soil exists or not.
The leaching time in the step (1) is preferably more than or equal to 7 days; more preferably 7 to 14 days; most preferably 14 days.
The soil sample in the step (1) is preferably a repaired soil sample; more preferably a soil sample that has been remediated by the high temperature curing technique.
The high-temperature curing technology comprises the following steps: mixing Cr2O3Mixing with heavy metal contaminated soil, adding auxiliary materials, and sintering at 900-1200 ℃ for 2-5 hours.
The heavy metal in the step (1) is preferably at least one of copper, zinc, lead, cadmium, nickel and chromium.
The pH gradient of the leaching agent in the step (1) is preferably more than or equal to 5; more preferably 6 or more.
The pH value range of the leaching agent is preferably 2-12.
The leaching agent comprises at least two alkaline leaching agents and at least two acidic leaching agents.
The pH of the lixiviant may be: 2.4, 6, 8, 10; 3.5, 7, 9, 11; 2.4, 6, 8, 10, 12, etc.
The preferable mass-volume ratio (g: mL) of the soil sample and the leaching agent in the step (1) is 1 (15-25); more preferably 1 (15-20).
The preparation method of the leaching agent refers to a solid waste leaching toxicity leaching method-sulfuric acid-nitric acid method (HJ/T299-2007), and specifically comprises the following steps: concentrated sulfuric acid and concentrated nitric acid are prepared into an initial solution according to the mass ratio of 2:1, and then deionized water and/or a sodium hydroxide solution are used for neutralizing to a specified target pH value.
The particle size of the soil sample is preferably <45 um.
The leaching method in step (1) is preferably as follows: shaking up and then overturning at the speed of 20-50 rpm.
The leaching concentration in step (1) is preferably determined by inductively coupled plasma emission spectroscopy.
The leaching concentration in the step (1) is preferably an average value of the leaching concentrations of heavy metals on the 7 th day and the 14 th day.
The method for measuring the acid dissolution state concentration of the heavy metal in the step (2) is as follows: and (2) mixing the soil sample leached in the step (1) with acid, oscillating, centrifuging to obtain supernatant, and determining the acid dissolution state concentration of the heavy metal.
The acid is preferably acetic acid.
And (2) cleaning and drying the extracted soil sample in the step (1) to obtain the extracted soil sample.
The oscillation condition in the step (2) is preferably oscillation for 15-20 hours at 23-28 ℃.
The centrifugation condition in the step (2) is preferably 8000-10000 r/min for 15-25 minutes.
The acid dissolved state concentration in step (2) is preferably determined by inductively coupled plasma emission spectroscopy.
The acid soluble state concentration in the step (2) is preferably the average value of the heavy metal acid soluble state concentrations of the soil samples leached for 7 days and 14 days in the step (1).
And (4) referring to relevant parameters and calculation models provided in technical guidelines for evaluating risks of soil pollution of construction sites (HJ25.3-2019) in the method for calculating the total carcinogenic risks and/or the hazard indexes in the step (4).
The total carcinogenic risk in step (4) is the sum of the carcinogenic risk of oral ingestion, the carcinogenic risk of transdermal ingestion, and the carcinogenic risk of ingestion of inhaled surface particulate matter.
The hazard index in the step (4) is the sum of the hazard quotient of oral intake, the hazard quotient of skin intake and the hazard quotient of intake of surface particulate matter by inhalation.
When the soil sample is taken from the first type of land (residential land),
the carcinogenic risk of Oral Ingestion (OISER)ca) The calculation formula of (a) is as follows:
the carcinogenic risk of percutaneous ingestion (DCSER)ca) The calculation formula of (a) is as follows:
the carcinogenic risk of ingestion of surface particulate matter by inhalation (PISER)ca) The calculation formula of (a) is as follows:
the oral intake jeopardizer (OISER)nc) The calculation formula of (a) is as follows:
the hazards of transdermal ingestion (DCSER)nc) The calculation formula of (a) is as follows:
the hazards of ingestion of surface particulate matter via inhalation (PISER)nc) The calculation formula of (a) is as follows:
when the soil sample is taken from a second type of land (industrial land),
the carcinogenic risk of Oral Ingestion (OISER)ca) The calculation formula of (a) is as follows:
the carcinogenic risk of percutaneous ingestion (DCSER)ca) The calculation formula of (a) is as follows:
the carcinogenic risk of ingestion of surface particulate matter by inhalation (PISER)ca) The calculation formula of (a) is as follows:
the oral intake jeopardizer (OISER)nc) The calculation formula of (a) is as follows:
the hazards of transdermal ingestion (DCSER)nc) The calculation formula of (a) is as follows:
the hazards of ingestion of surface particulate matter via inhalation (PISER)nc) The calculation formula of (a) is as follows:
the relevant exposure parameters and reference values calculated by the above carcinogenic risk/hazard quotient are as follows:
the non-carcinogenic doses and carcinogenic slope factors for different heavy metals in the above carcinogenic risk/hazard quotient calculations are as follows:
the evaluation method in the step (5) refers to the evaluation criteria provided in technical guidelines for evaluating soil pollution risks in construction sites (HJ25.3-2019), and specifically includes the following steps: acceptable total carcinogenic risk level for a single contaminant is 10-6(ii) a Acceptable hazard index for single contaminants is 1; and (3) when the calculated result (total carcinogenic risk and/or hazard index of the heavy metal in the soil sample) in the step (4) is greater than the acceptable risk level, indicating that the heavy metal human health risk exists.
The invention also provides application of the method for evaluating the human health risk of the heavy metal contaminated soil in the field of environmental monitoring.
The invention has the beneficial effects that:
1. the method adopts two procedures of leaching agent leaching and acid dissolution state extraction, comprehensively considers the leaching concentration of the soil and the acid dissolution state concentration, and effectively overcomes the defect that the traditional heavy metal leaching toxicity leaching evaluation method only considers the leaching concentration of the heavy metal under a specific pH condition (usually a strong acid condition) and within a specific reaction time period as an evaluation standard. The method effectively avoids the possibility of underestimating the human health risk of the repaired soil under the neutral or slightly alkaline condition and overestimating the human health risk of the unrepaired soil under the neutral or slightly alkaline condition, which are possibly generated by the traditional heavy metal leaching toxicity leaching evaluation method, and effectively reduces the uncertainty of the human health risk evaluation of the repaired soil.
2. According to the method, the risk concentration of the heavy metal in the repaired soil can be effectively calculated by constructing the functional relationship C1(pH) between the leaching concentration of the heavy metal in the soil sample and the pH value of the leaching agent and the functional relationship C2(pH) between the acid dissolved state concentration of the heavy metal in the soil sample and the pH value of the leaching agent, so that the human health risk of the heavy metal in the repaired soil can be further calculated quantitatively. The method is based on the heavy metal solidification mechanism, comprehensively considers the leaching concentration and the acid dissolution state concentration of the soil, is stricter and more accurate compared with the traditional single toxicity leaching evaluation method, can effectively evaluate the human health risks possibly generated by the repaired soil under the complex pH environmental conditions of different practical recycling situations, and realizes the dynamic evaluation of the human health risks recycled after the heavy metal polluted soil is repaired under the different pH environmental conditions.
3. According to the method, the leaching concentration and the acid dissolved state concentration of the soil are obtained in sequence, the risk concentration possibly generated by the heavy metal contaminated soil is calculated, and then the human health risk possibly generated when the restored soil is reused in the first type land (residential life land) and the second type land (industrial land) is quantitatively evaluated according to parameters and calculation models provided by 'construction land soil pollution risk assessment technical guide (HJ 25.3-2019)' which is newly introduced in China. The method has wide applicability, and can be applied to quantitative evaluation of human health risks of heavy metals in soil and unrepaired soil after remediation under different pH value environmental conditions in different regions of the country.
Drawings
FIG. 1 is a graph of the change in leaching concentration of Zn at different pH of leaching agents for soil after remediation and soil without remediation in example 1: wherein A is a leaching concentration change diagram of Zn of the repaired soil under leaching agents with different pH values; and B is a leaching concentration change chart of Zn of the unrepaired soil under leaching agents with different pH values.
FIG. 2 is a graph of the change in acid dissolved state concentration of Zn at different pH of lixiviants for the soil after remediation and for the soil without remediation of example 1: wherein A is an acid soluble state concentration change diagram of Zn of the repaired soil under leaching agents with different pH values; and B is a graph of the change of the acid soluble state concentration of Zn of the unrepaired soil under the condition of leaching agents with different pH values.
FIG. 3 is a graph of the second order polynomial fit of the Zn leaching concentration and the acid dissolved state concentration, respectively, to the leaching agent pH in example 1: wherein A is a quadratic polynomial fitting relation graph of the leaching concentration of Zn in the repaired soil and the pH value of the leaching agent; b is a quadratic polynomial fitting relation graph of the leaching concentration of Zn in the unrepaired soil and the pH value of the leaching agent; c is a quadratic polynomial fitting relation graph of the acid soluble state concentration of Zn in the restored soil and the pH value of the leaching agent; d is a quadratic polynomial fitting relation graph of the acid soluble state concentration of Zn in the unrepaired soil and the pH value of the leaching agent.
FIG. 4 is a graph of hazard indices for Zn at different pH's in example 1: wherein A is a hazard index chart of Zn under different pH values when the soil is used for a first land; and B is a hazard index chart of Zn at different pH values when the soil is used for the second land.
FIG. 5 is a graph of the change in leaching concentration of Cu at different pH of leachants for soil after remediation and for unrepaired soil of example 2: wherein A is a leaching concentration change diagram of Cu of the soil after remediation under different pH leaching agents; and B is a leaching concentration change graph of Cu of unrepaired soil under leaching agents with different pH values.
FIG. 6 is a graph of the change in the acid soluble state concentration of Cu at different pH of lixiviants for the soil after remediation and for the soil without remediation of example 2: wherein A is an acid soluble state concentration change diagram of Cu of the repaired soil under lixiviants with different pH values; and B is a graph of the change of the acid soluble state concentration of Cu of the unrepaired soil under different pH lixiviants.
FIG. 7 is a second order polynomial fit of the leaching concentration and acid soluble state concentration of Cu, respectively, to the pH of the leaching agent in example 2: wherein A is a quadratic polynomial fitting relation graph of the leaching concentration of Cu in the repaired soil and the pH value of the leaching agent; b is a quadratic polynomial fitting relation graph of the leaching concentration of Cu in the unrepaired soil and the pH value of the leaching agent; c is a quadratic polynomial fitting relation graph of acid soluble state concentration of Cu in the repaired soil and the pH value of the leaching agent; d is a quadratic polynomial fitting relation graph of the acid soluble state concentration of Cu in the unrepaired soil and the pH value of the leaching agent.
FIG. 8 is a graph of hazard indices for Cu at different pH's in example 2: wherein A is a hazard index diagram of Cu under different pH values when the soil is used for a first land; and B is a hazard index graph of Cu at different pH values when the soil is used for land of the second type.
FIG. 9 is a graph of the change in Cd leach concentrations at different pH leachants for soil after remediation and for non-remediated soil of example 3: wherein A is a leaching concentration change diagram of Cd of the repaired soil under leaching agents with different pH values; and B is a leaching concentration change diagram of Cd of unrepaired soil under leaching agents with different pH values.
FIG. 10 is a graph of the change in acid solution concentration of Cd at different pH of lixiviants for the soil after remediation and the soil without remediation of example 3: wherein A is an acid dissolution state concentration change diagram of Cd of the restored soil under lixiviants with different pH values; and B is an acid soluble state concentration change diagram of Cd of unrepaired soil under lixiviants with different pH values.
FIG. 11 is a graph of the quadratic polynomial fit of the concentrations of Cd and acid soluble state to the lixiviant pH in example 3, respectively: wherein A is a quadratic polynomial fitting relation graph of the leaching concentration of Cd in the restored soil and the pH value of a leaching agent; b is a quadratic polynomial fitting relation graph of the leaching concentration of Cd in the unrepaired soil and the pH value of the leaching agent; c is a quadratic polynomial fitting relation graph of the acid soluble state concentration of Cd in the restored soil and the pH value of the leaching agent; d is a quadratic polynomial fitting relation graph of the acid soluble state concentration of Cd in the unrepaired soil and the pH value of the leaching agent.
FIG. 12 is a plot of hazard indices for Cd in example 3 at different pH: wherein A is a hazard index diagram of Cd under different pH values when the soil is used for a first land; and B is a hazard index diagram of Cd at different pH values when the soil is used for second-class land.
Fig. 13 is a graph of the total carcinogenic risk of Cd at different pH in example 3: wherein, A is a total carcinogenic risk map of Cd under different pH values when the soil is used for a first kind of land; b is the total carcinogenic risk profile of Cd at different pH when the soil was used for land of the second type.
Detailed Description
The present invention will be described in further detail with reference to the following specific embodiments and accompanying drawings.
The materials, reagents and the like used in the present examples are commercially available reagents and materials unless otherwise specified.
Example 1 evaluation method of human health risks of Zinc (Zn) contaminated soil
This example uses a laboratory to simulate heavy metal contaminated soil. The pollution-free soil is collected from green land of a certain park in a Tianhe area of Guangzhou city, the surface soil with the surface layer of 30cm is adopted, the pH value of the soil is 5.4, the concentration of Zn in the pollution-free soil is 27.7mg/kg, ZnO powder is added manually, and the Zn content in the pollution soil reaches 3413.7mg/kg after the pollution-free soil is fully ground; by adding Cr2O3Form ZnCr2O4High-temperature solidification reaction by way of spinel, ZnO and Cr2O3According to the molar ratio of Zn: cr was prepared in a 1:2 manner. And then adding coal gangue and shale into the mixed contaminated soil as auxiliary materials, wherein the mass ratio of the coal gangue to the shale in the auxiliary materials is 1:2, and the mass ratio of the auxiliary materials to the contaminated soil is 2: 1. And pressing the fully mixed and ground sample into a cylindrical sample under 350MPa, sintering the cylindrical sample in a muffle furnace at 1000 ℃ for 4 hours to obtain a soil sample repaired by a high-temperature curing technology, and using the soil sample for human health risk assessment in the next Zn-contaminated soil repairing and recycling process. Meanwhile, a soil sample which is not repaired by the high-temperature curing technology is analyzed, and the human health risk assessment method of the unrepaired soil is the same as the soil assessment method after high-temperature curing repair.
The method for evaluating the human health risk of the heavy metal contaminated soil in the embodiment comprises the following steps:
(1) firstly, both a restored soil sample and an unrepaired soil sample are ground into particle sizes<45um fine powder, 6 leaching agents with different pH value gradients (pH values are 2, 4, 6, 8, 10 and 12) are prepared for leaching the soil after high-temperature curing and repairing. The preparation of the leaching agent refers to a solid waste leaching toxicity leaching method-sulfuric acid-nitric acid method (HJ/T299-2007) in China, concentrated sulfuric acid and concentrated nitric acid adopt a mass ratio of 2:1 to prepare an initial solution, and then the initial solution is usedDeionized water and sodium hydroxide solution were neutralized in appropriate amounts to the indicated target pH. Then 0.5g of powder sample of the repaired soil and the unrepaired soil is respectively poured into a centrifuge tube filled with 10mL of leaching agent, the powder samples are fully shaken up and then are subjected to a turnover experiment at the speed of 30rpm, and the samples are sequentially sampled at the 1d, 3d, 7d, 14d, 21d, 28d, 42d and 56d in the experiment process for 8 times in total. Finally, the lixiviant samples of the restored soil and the unrepaired soil are filtered by a 0.25um cellulose membrane, and the equilibrium leaching concentration C1 of Zn in the samples is measured by an inductively coupled plasma emission spectrometer (ICP-OES), and the result is shown in figure 1: for the unrepaired soil samples, the leaching concentration of Zn increased from day 1 until day 7 and gradually stabilized, and the equilibrium leaching concentration decreased gradually with the increase in pH of the leaching agent, and the equilibrium leaching concentration C1 (average of heavy metal leaching concentrations at day 7 and day 14) of Zn after reaching stabilization decreased from 1315.8mg/kg at pH 2 to 3.94mg/kg (pH 4), 1.87mg/kg (pH 6), 2.18mg/kg (pH 8), 1.01mg/kg (pH 10) and 9.06mg/kg (pH 12); after remediation by the high temperature solidification technique, Zn in the artificially prepared heavy metal heavily contaminated soil sample was well immobilized, and the equilibrium leaching concentration C1 of Zn was reduced from 5.98mg/kg at pH 2 to 1.95mg/kg (pH 4), 1.14mg/kg (pH 6), 0.96mg/kg (pH 8), 1.12mg/kg (pH 10) and 1.13mg/kg (pH 12). Compared with the unrepaired soil sample, the average leaching concentration of Zn in the restored soil sample is reduced by 119-432 times. The leaching concentration of Zn in the repaired soil sample is far lower than the risk screening value (Zn) for repairing the soil of the Chinese heavy metal polluted residential area<500mg/kg, DB 43/T1165). The functional relationship between the equilibrium leaching concentration of Zn in the soil after remediation and the pH value of the leaching agent can be established through quadratic polynomial fitting, and the result is shown in figure 3-A: the specific fitting formula is as follows: c1-0.11 pH2-1.90pH+8.78，R2The fitting effect is better when the value is 0.91. Similarly, the function relationship between the equilibrium leaching concentration of Zn in the unrepaired soil and the pH value of the leaching agent can be established by quadratic polynomial fitting, and the result is shown in FIG. 3-B: the specific fitting formula is as follows: c1 ═ 0.03pH2+0.54pH+0.01，R2The fitting effect is better when the value is equal to 0.66.
(2) Different pH values after completion of the first stepAfter the leaching experiment under the leaching agent, the leached restored soil sample and the leached unrepaired soil sample are respectively washed by deionized water and dried, and then are moved into a 50ml centrifugal tube for carrying out the acid dissolution state extraction experiment. The specific extraction process is as follows: the leached restored soil sample and the leached unrepaired soil sample are respectively added into 20mL of 0.11mol/L acetic acid solution, the mixture is shaken at the room temperature of 25 ℃ for 18 hours, then the mixture is centrifuged in a centrifuge with 9000r/min for 20 minutes, the supernatant is transferred to a 10mL centrifuge tube, and the acid dissolution state concentration of Zn is measured by ICP-OES. The results are shown in FIG. 2: the average concentration C2 of the acid-soluble state of Zn (average value of the concentration of the heavy metal acid-soluble state on day 7 and 14) in the soil sample after remediation was 2.216mg/kg (pH 2), 2.60mg/kg (pH 4), 3.08mg/kg (pH 6), 3.35mg/kg (pH 8), 4.53mg/kg (pH 10), and 3.21mg/kg (pH 12), in that order; the samples of the unrepaired soil were 1282.48mg/kg (pH 2), 1409.65mg/kg (pH 4), 1441.02mg/kg (pH 6), 1422.92mg/kg (pH 8), 1448.08mg/kg (pH 10) and 1423.09mg/kg (pH 12) in that order. It is clear that the acid solution concentration of the soil after remediation by the high temperature remediation technique is significantly less than that of the unrepaired soil. The functional relationship between the concentration of the dissolved state of the Zn acid in the soil after remediation and the pH value of the leaching agent can be established through quadratic polynomial fitting, and the result is shown in a figure 3-C: the specific fitting formula is as follows: c2 ═ 0.03pH2+0.54pH+0.01，R2The fitting effect is better when the value is equal to 0.66. Similarly, the functional relationship between the concentration of the Zn acid in the unrepaired soil in the dissolved state and the pH of the leaching agent can be established by quadratic polynomial fitting, and the result is shown in FIG. 3-D: the specific fitting formula is as follows: c2 ═ 3.51pH2+60.53pH+1193.6，R2＝0.75。
(3) Carrying out combined analysis on the equilibrium leaching concentration C1 of Zn in the repaired soil and the acid dissolution state concentration C2 of Zn in the repaired soil to obtain the human health risk concentration C of Zn in the soilriskThe specific calculation formula is as follows: crisk＝0.5×C1+0.5×C2。
(4) The obtained human health risk concentration CriskSubstituting into the calculation model provided in the technical guide of evaluating the risk of soil pollution in construction land (HJ25.3-2019) newly introduced in China to obtainThe total carcinogenic risk and/or hazard index of heavy metals in soil, the calculation model is as follows:
the formula for the carcinogenic risk and hazard quotient for the first type of land (residential land) is as follows:
carcinogenic risk by Oral Ingestion (OISER)ca) And harmfulness quotient (OISER)nc)：
Carcinogenic risk by percutaneous ingestion (DCSER)ca) And hazard quotient (DCSER)nc)：
Carcinogenic risk of ingestion of surface particulate matter by inhalation (PISER)ca) And hazard quotient (PISER)nc)：
Hazard index ═ OISERnc+DCSERnc+PISERnc；
Total carcinogenic risk ═ OISERca+DCSERca+PISERca。
The formula for the carcinogenic risk and hazard quotient for the second type of land (industrial land) is:
carcinogenic risk by Oral Ingestion (OISER)ca) And harmfulness quotient (OISER)nc)：
Carcinogenic risk by percutaneous ingestion (DCSER)ca) And hazard quotient (DCSER)nc)：
Carcinogenic risk of ingestion of surface particulate matter by inhalation (PISER)ca) And hazard quotient (PISER)nc)：
Hazard index ═ OISERnc+DCSERnc+PISERnc；
Total carcinogenic risk ═ OISERca+DCSERca+PISERca。
The related parameters in the calculation formula of the carcinogenic risk/harm quotient of the two types of land are shown in tables 1 and 2. Meanwhile, the total carcinogenic risk and/or hazard index of the soil heavy metal obtained by calculation is calculated according to the evaluation standard provided in technical guidelines for evaluating the risk of soil pollution of construction land (HJ25.3-2019)And (3) carrying out risk rating: acceptable total carcinogenic risk level for a single contaminant is 10-6(ii) a Acceptable hazard index for single contaminants is 1; when the calculated result (total carcinogenic risk and/or hazard index of heavy metals in the soil sample) is greater than the acceptable risk level, it indicates that there is a human health risk of heavy metals. The heavy metal in this example is zinc, and the results are shown in fig. 4: sintered samples treated by the high temperature solidification technique (soil samples after remediation) have a significantly lower hazard index of Zn than non-sintered samples (soil samples not under remediation), with the hazard index of Zn gradually decreasing for both the remediated and non-remediated soil samples as the pH value gradually increases: for the residential site scene, the hazard indexes of Zn of the unrepaired soil samples at the pH values of 2, 4, 6, 8, 10 and 12 are respectively 4.71E-02, 2.56E-02, 2.61E-02, 2.58E-02, 2.62E-02 and 2.59E-02; after remediation, the hazard index of Zn of the soil sample at the pH values of 2, 4, 6, 8, 10 and 12 is respectively reduced to 1.47E-04, 8.25E-04, 7.65E-04, 7.82E-04, 1.01E-04 and 7.87E-05; for industrial site scenes, the hazard indexes of Zn of unrepaired soil samples at pH values of 2, 4, 6, 8, 10 and 12 are 5.72E-03, 3.11E-03, 3.17E-03, 3.13E-03, 3.19E-03 and 3.15E-03 respectively; after the soil sample is repaired by a high-temperature curing technology, the hazard indexes of Zn are respectively reduced to 1.79E-05, 1.00E-05, 9.29E-06, 9.49E-06, 1.22E-05 and 9.55E-06 when the pH value of the soil sample is 2, 4, 6, 8, 10 and 12; namely, the harm index of Zn in the unrepaired soil sample is well reduced by the high-temperature curing treatment technology; by the method, the possibility of underestimating the heavy metal hazard index of the repaired soil under neutral and alkaline conditions is effectively avoided, the possibility of overestimating the heavy metal hazard index of the unrepaired soil under neutral and alkaline conditions is also avoided, and the quantitative and accurate evaluation of the human health risk of the soil after heavy metal repair in the recycling process is realized.
Table 1 carcinogenic risk/hazard quotient calculated relevant exposure parameters and reference values
TABLE 2 non-carcinogenic dose and carcinogenic slope factor for different heavy metals
Example 2 evaluation method for human health risks of copper (Cu) -contaminated soil
This example uses a laboratory to simulate heavy metal contaminated soil. The pollution-free soil is collected from green land of a certain park in a Tianhe area of Guangzhou city, the surface soil with the surface layer of 30cm is adopted, the pH value of the soil is 5.6, the concentration of Cu in the pollution-free soil is 15.2mg/kg, CuO powder is manually added, and the Cu content in the pollution soil reaches 4656.4mg/kg after full grinding; by adding Cr2O3Form CuCr2O4High-temperature solidification reaction is carried out in a spinel mode, and CuO and Cr2O3The molar ratio of Cu: cr was prepared in a 1:2 manner. And then adding coal gangue and shale into the mixed contaminated soil as auxiliary materials, wherein the mass ratio of the coal gangue to the shale in the auxiliary materials is 1:2, and the mass ratio of the auxiliary materials to the contaminated soil is 2: 1. And pressing the fully mixed and ground sample into a cylindrical sample under 350MPa, sintering the cylindrical sample in a muffle furnace at 1000 ℃ for 4 hours to obtain a soil sample repaired by a high-temperature curing technology, and using the soil sample for human health risk assessment in the next Cu-polluted soil repairing and recycling process. Meanwhile, a soil sample which is not repaired by the high-temperature curing technology is analyzed, and the calculation method of the human health risk of the unrepaired soil is the same as the calculation method of the soil which is repaired by the high-temperature curing technology.
The method for evaluating the human health risk of the heavy metal contaminated soil in the embodiment comprises the following steps:
(1) firstly, both a restored soil sample and an unrepaired soil sample are ground into particle sizes<45um fine powder, 6 leaching agents with different pH value gradients (pH values are 2, 4, 6, 8, 10 and 12) are prepared for leaching the soil after high-temperature curing and repairing. Formulation reference of leaching agentIn the 'solid waste leaching toxicity leaching method-sulfuric acid-nitric acid method' (HJ/T299-2007) of China, concentrated sulfuric acid and concentrated nitric acid are prepared into an initial solution in a mass ratio of 2:1, and then deionized water and a sodium hydroxide solution are used for carrying out appropriate neutralization to a specified target pH value. Then 0.5g of powder sample of the repaired soil and the unrepaired soil is respectively poured into a centrifuge tube filled with 10mL of leaching agent, the powder samples are fully shaken up and then are subjected to a turnover experiment at the speed of 30rpm, and the samples are sequentially sampled at the 1d, 3d, 7d, 14d, 21d, 28d, 42d and 56d in the experiment process for 8 times in total. Finally, the lixiviant samples of the restored soil and the unrepaired soil were filtered through a 0.25um cellulose membrane, and the equilibrium leaching concentration C1 of Cu in the samples was measured by an inductively coupled plasma emission spectrometer (ICP-OES), and the results are shown in fig. 5: for the unrepaired soil samples, the equilibrium leaching concentration C1 of Cu (average of heavy metal leaching concentrations at day 7 and day 14) was reduced from 63.94mg/kg at pH 2 to 2.85mg/kg (pH 4), 0.18mg/kg (pH 6), 0.15mg/kg (pH 8), 1.09mg/kg (pH 10) and 0.68mg/kg (pH 12); after restoration by the high temperature curing technique, the artificially prepared heavy metal heavily contaminated soil sample was well fixed with Cu, and the average leaching concentration of Cu was reduced from 26.40mg/kg at pH 2 to 0.23mg/kg (pH 4), 0.25mg/kg (pH 6), 0.21mg/kg (pH 8), 0.23mg/kg (pH 10) and 0.56mg/kg (pH 12). The average leaching concentration of Cu in the remediated soil sample was significantly reduced compared to the unrepaired soil sample. The functional relationship between the equilibrium leaching concentration of Cu in the soil after remediation and the pH value of the leaching agent can be established through quadratic polynomial fitting, and the result is shown in figure 7-A: the specific fitting formula is as follows: c1-0.59 pH2-10.13pH+39.65，R2The fitting effect is better when the value is equal to 0.79. Similarly, the equilibrium leaching concentration of Cu in the unrepaired soil as a function of the pH of the leaching agent can be established by quadratic polynomial fitting, and the results are shown in FIG. 7-B: the specific fitting formula is as follows: c1 ═ 1.42pH2-24.46pH+96.62，R2The fitting effect is better when the value is 0.81.
(2) After the leaching experiment under different pH values of leaching agents in the first step is finished, leaching the repaired soil sample and leaching the unrepaired soil sample by using deionized waterAfter washing and drying, the mixture was transferred into a 50ml centrifuge tube for an acid solution state extraction experiment. The specific extraction process is as follows: the leached restored soil sample and the leached unrepaired soil sample are respectively ground to 100 meshes, 20mL of 0.11mol/L acetic acid solution is added, the mixture is shaken at the room temperature of 25 ℃ for 18 hours, then the mixture is centrifuged in a centrifuge with 9000r/min for 20 minutes, the supernatant is transferred to a 10mL centrifuge tube, and the acid dissolution state concentration of Cu is measured by ICP-OES. The results are shown in FIG. 6: the acid-soluble average concentration C2 (average of heavy metal acid-soluble concentrations on day 7 and day 14) of Cu in the soil sample after remediation was 9.21mg/kg (pH 2), 21.91mg/kg (pH 4), 23.34mg/kg (pH 6), 22.90mg/kg (pH 8), 22.33mg/kg (pH 10), and 32.23mg/kg (pH 12) in this order; the samples of the unrepaired soil were 347.13mg/kg (pH 2), 238.74mg/kg (pH 4), 251.64mg/kg (pH 6), 225.22mg/kg (pH 8), 224.18mg/kg (pH 10) and 257.46mg/kg (pH 12) in that order. It is clear that the acid solution concentration of the soil after remediation by the high temperature remediation technique is significantly less than that of the unrepaired soil. The functional relationship between the concentration of the dissolved state of the Cu acid in the soil after remediation and the pH value of the leaching agent can be established through quadratic polynomial fitting, and the result is shown in figure 7-C: the specific fitting formula is as follows: c2-0.10 pH2+3.03pH+6.73，R2The fitting effect is better when the value is equal to 0.72. Similarly, the functional relationship between the concentration of the dissolved state of Cu acid in the unrepaired soil and the pH of the leaching agent can be established by quadratic polynomial fitting, and the results are shown in FIG. 7-D: the specific fitting formula is as follows: c2-2.91 pH2-48.19pH+418，R2＝0.82。
(3) Carrying out combined analysis on the equilibrium leaching concentration C1 of Cu in the repaired soil and the acid dissolution state concentration C2 of Cu in the repaired soil to obtain the human health risk concentration C of Cu in the repaired soilriskThe specific calculation formula is as follows: crisk＝0.5×C1+0.5×C2。
(4) The obtained human health risk concentration CriskThe total carcinogenic risk and/or hazard index of the heavy metals in the soil are calculated and obtained by substituting the calculation model provided in the technical guide for evaluating the risk of soil pollution in construction sites (HJ25.3-2019) newly introduced in China (the calculation model and related parameters refer to embodiment 1).And simultaneously, carrying out risk rating on the total carcinogenic risk and/or hazard index of the heavy metal in the soil obtained by calculation according to evaluation criteria provided in technical guidelines for evaluating the risk of soil pollution of construction land (HJ 25.3-2019): acceptable total carcinogenic risk level for a single contaminant is 10-6(ii) a Acceptable hazard index for single contaminants is 1; when the calculated result (total carcinogenic risk and/or hazard index of heavy metals in the soil sample) is greater than the acceptable risk level, it indicates that there is a human health risk of heavy metals. The heavy metal in this example is copper, and the results are shown in FIG. 8: the hazard index of Cu of the sintered samples (soil samples after remediation) treated by the high temperature solidification technique is significantly lower than that of the non-sintered samples (soil samples without remediation), and as the pH value gradually increases, the hazard index of Cu of the soil samples with remediation and non-remediation gradually decreases: for the residential site scene, the hazard indexes of Cu of the unrepaired soil samples at the pH values of 2, 4, 6, 8, 10 and 12 are 5.57E-02, 3.27E-02, 3.41E-02, 3.05E-02 and 3.50E-02 respectively; after the remediation, the hazard indexes of Cu of the soil sample at the pH values of 2, 4, 6, 8, 10 and 12 are respectively reduced to 4.83E-03, 3.00E-03, 3.20E-03, 3.13E-03, 3.06E-03 and 4.44E-03; for industrial site scenes, the hazard indexes of Cu of unrepaired soil samples at pH values of 2, 4, 6, 8, 10 and 12 are 6.73E-03, 3.96E-03, 4.12E-03, 3.69E-03 and 4.23E-03 respectively; after the soil sample is repaired by a high-temperature curing technology, the hazard indexes of Cu are respectively reduced to 5.83E-04, 3.62E-04, 3.86E-04, 3.78E-04, 3.69E-05 and 4.23E-04 when the pH value of the soil sample is 2, 4, 6, 8, 10 and 12; namely, the harm index of Cu in the unrepaired soil sample is well reduced by the high-temperature curing treatment technology; by the method, the possibility of underestimating the heavy metal hazard index of the repaired soil under neutral and alkaline conditions is effectively avoided, the possibility of overestimating the heavy metal hazard index of the unrepaired soil under neutral and alkaline conditions is also avoided, and the quantitative and accurate evaluation of the human health risk of the soil after heavy metal repair in the recycling process is realized.
Example 3 evaluation method for human health risks of cadmium (Cd) contaminated soil
The embodiment adopts a laboratory to simulate the heavy metal polluted soilSoil is prepared. The pollution-free soil is collected from green land of a certain park in a Tianhe area of Guangzhou city, the surface soil with the surface layer of 30cm is adopted, the pH value of the soil is 5.6, the concentration of Cd in the pollution-free soil is 0.019mg/kg, CdO powder is added manually, and the content of Cd in the pollution soil is 8412.6mg/kg after full grinding; by adding Cr2O3Form CdCr2O4High-temperature solidification reaction is carried out by means of spinel, and CdO and Cr2O3The method adopts the following steps that (1) the molar ratio of Cd: cr was prepared in a 1:2 manner. And then adding coal gangue and shale into the mixed contaminated soil as auxiliary materials, wherein the mass ratio of the coal gangue to the shale in the auxiliary materials is 1:2, and the mass ratio of the auxiliary materials to the contaminated soil is 2: 1. And pressing the fully mixed and ground sample into a cylindrical sample under 350MPa, sintering the cylindrical sample in a muffle furnace at 1000 ℃ for 4 hours to obtain a soil sample repaired by a high-temperature curing technology, and evaluating the human health risk in the next process of repairing the Cd-polluted soil and then recycling the Cd-polluted soil. Meanwhile, a soil sample which is not repaired by the high-temperature curing technology is analyzed, and the calculation method of the human health risk of the unrepaired soil is the same as the calculation method of the soil which is repaired by the high-temperature curing technology.
The method for evaluating the human health risk of the heavy metal contaminated soil in the embodiment comprises the following steps:
(1) firstly, both a restored soil sample and an unrepaired soil sample are ground into particle sizes<45um fine powder, 6 leaching agents with different pH value gradients (pH values are 2, 4, 6, 8, 10 and 12) are prepared for leaching the soil after high-temperature curing and repairing. The preparation of the leaching agent refers to a solid waste leaching toxicity leaching method-sulfuric acid-nitric acid method (HJ/T299-2007) in China, concentrated sulfuric acid and concentrated nitric acid adopt a mode with a mass ratio of 2:1 to prepare an initial solution, and then deionized water and a sodium hydroxide solution are used for carrying out appropriate neutralization to a specified target pH value. Then 0.5g of powder sample of the repaired soil and the unrepaired soil is respectively poured into a centrifuge tube filled with 10mL of leaching agent, the powder samples are fully shaken up and then are subjected to a turnover experiment at the speed of 30rpm, and the samples are sequentially sampled at the 1d, 3d, 7d, 14d, 21d, 28d, 42d and 56d in the experiment process for 8 times in total. Finally, leaching agent samples of the restored soil and unrepaired soil samples are obtainedThe equilibrium leaching concentration C1 of Cd in the sample was measured by inductively coupled plasma emission spectroscopy (ICP-OES) after filtration on a 0.25um cellulose membrane, and the results are shown in FIG. 9: for the unrepaired soil samples, the equilibrium leaching concentration of Cd (average of heavy metal leaching concentrations at day 7 and day 14) was reduced from 2245.81mg/kg at pH 2 to 14.09mg/kg (pH 4), 9.26mg/kg (pH 6), 7.88mg/kg (pH 8), 4.44mg/kg (pH 10) and 16.71mg/kg (pH 12); after restoration by the high-temperature curing technology, Cd in the heavy metal heavily polluted soil sample prepared by the manual method is well fixed, and the equilibrium leaching concentration of Cd is reduced from 6.14mg/kg at pH 2 to 4.51mg/kg (pH 4), 1.52mg/kg (pH 6), 1.62mg/kg (pH 8), 2.67mg/kg (pH 10) and 1.26mg/kg (pH 12). Compared with the unrepaired soil sample, the equilibrium leaching concentration of Cd in the restored soil sample is obviously reduced. The functional relationship between the equilibrium leaching concentration of Cd in the soil after remediation and the pH value of the leaching agent can be established through quadratic polynomial fitting, and the result is shown in FIG. 11-A: the specific fitting formula is as follows: c1-0.08 pH2-1.51pH+8.82，R2The fitting effect is better when the value is 0.83. Similarly, a functional relationship between equilibrium leaching concentration of Cd in the unrepaired soil and the pH of the leaching agent can be established by quadratic polynomial fitting, and the results are shown in FIG. 11-B: the specific fitting formula is as follows: c1-50.11 pH2-861.25pH+3371.5，R2The fitting effect is better when the value is equal to 0.79.
(2) After the leaching experiment under different pH values of the leaching agent in the first step is finished, the leached repaired soil sample and the leached unrepaired soil sample are respectively washed by deionized water and dried, and then are moved into a 50ml centrifugal tube for carrying out an acid dissolution state extraction experiment. The specific extraction process is as follows: respectively grinding the leached restored soil sample and the leached unrepaired soil sample to 100 meshes, adding 20mL of 0.11mol/L acetic acid solution, oscillating at 25 ℃ for 18 hours at room temperature, then centrifuging for 20 minutes in a centrifugal machine at 9000r/min, transferring the supernatant into a 10mL centrifugal tube, and determining the acid dissolution state content of Cd by using ICP-OES. The results are shown in FIG. 10: the average concentration C2 of the Cd acid dissolved state in the soil sample after remediation (average value of the concentration of the heavy metal acid dissolved state on the 7 th day and the 14 th day) is 7.60mg/kg (pH 2) and 9.53mg/kg (pH 4), 15.21mg/kg (pH 6), 15.58mg/kg (pH 8), 15.40mg/kg (pH 10) and 17.52mg/kg (pH 12); the average concentration of Cd in acid-soluble state in the unrepaired soil samples was 1959.50mg/kg (pH 2), 2484.51mg/kg (pH 4), 2459.48mg/kg (pH 6), 2620.53mg/kg (pH 8), 2418.96mg/kg (pH 10) and 2397.42mg/kg (pH 12) in this order. It is clear that the acid solution concentration of the soil after remediation by the high temperature remediation technique is significantly less than that of the unrepaired soil. The functional relationship between the concentration of the dissolved state of Cd acid in the soil after remediation and the pH value of the leaching agent can be established through quadratic polynomial fitting, and the result is shown in FIG. 11-C: the specific fitting formula is as follows: c2 ═ pH2+2.37pH+2.96，R2The fitting effect is better when the value is equal to 0.78. Similarly, a functional relationship between the concentration of the dissolved state of Cd acid in the unrepaired soil and the pH of the leaching agent can be established by quadratic polynomial fitting, and the results are shown in FIG. 11-D: the specific fitting formula is as follows: c2 ═ 15.35pH2+245.7pH+1601.5，R2The fitting effect is better when the value is equal to 0.66.
(3) Carrying out combined analysis on the equilibrium leaching concentration C1 of Cd in the restored soil and the acid dissolution state concentration C2 of Cd in the restored soil to obtain the human health risk concentration C of Cd in the restored soilriskThe specific calculation formula is as follows: crisk＝0.5×C1+0.5×C2。
(4) The obtained human health risk concentration CriskThe total carcinogenic risk and/or hazard index of heavy metals in soil is calculated and obtained by a calculation model provided in technical guidance for evaluating the risk of soil pollution in construction sites (HJ25.3-2019) newly introduced in China (the calculation model and related parameters refer to embodiment 1). And simultaneously, carrying out risk rating on the total carcinogenic risk and/or hazard index of the heavy metal in the soil obtained by calculation according to evaluation criteria provided in technical guidelines for evaluating the risk of soil pollution of construction land (HJ 25.3-2019): acceptable total carcinogenic risk level for a single contaminant is 10-6(ii) a Acceptable hazard index for single contaminants is 1; when the calculated result (total carcinogenic risk and/or hazard index of heavy metals in the soil sample) is greater than the acceptable risk level, it indicates that there is a human health risk of heavy metals. The heavy metal in this example is cadmium, so the results are shown in FIGS. 12 and 13The following steps: the hazard index of Cd of a sintered sample (a soil sample after restoration) treated by a high-temperature curing technology is significantly lower than that of an unsintered sample (an unrepaired soil sample), and the hazard index of Cd of the soil sample after restoration and unrepaired is gradually reduced along with the gradual rise of the pH value: for the residential land scene, the hazard indexes of Cd of an unrepaired soil sample at pH values of 2, 4, 6, 8, 10 and 12 are 7.37, 3.97, 3.93, 4.01, 3.84 and 3.92 respectively; after the remediation, the hazard index of Cd of the soil sample at the pH values of 2, 4, 6, 8, 10 and 12 is respectively reduced to 2.60E-01, 2.66E-01, 3.17E-01, 3.26E-01, 3.42E-01 and 3.56E-01; for industrial site scenes, the hazard indexes of Cd at pH values of 2, 4, 6, 8, 10 and 12 of an unrepaired soil sample are 1.67, 9.01, 8.91, 9.10, 8.71 and 8.88 respectively; after the soil sample is repaired by a high-temperature curing technology, the hazard indexes of Cd are respectively reduced to 5.90E-02, 6.03E-02, 7.18E-02, 7.39E-02, 7.76E-02 and 8.07E-02 when the pH value of the soil sample is 2, 4, 6, 8, 10 and 12; namely, the hazard index of Cd in the unrepaired soil sample is well reduced by the high-temperature curing treatment technology, so that the soil sample with heavy metal human health risk is converted into the soil sample without heavy metal human health risk; for the residential land scene, the total carcinogenic risk of Cd at pH values of 2, 4, 6, 8, 10 and 12 for the unrepaired soil samples is as follows: 7.97E-05, 4.30E-05, 4.25E-05, 4.35E-05, 4.16E-05 and 4.24E-05; the total carcinogenic risk of Cd in the repaired soil is as follows in sequence: 2.82E-07, 2.88E-07, 3.43E-07, 3.53E-07, 3.71E-07 and 3.85E-07; for industrial sites, the total carcinogenic risk of Cd at pH values of 2, 4, 6, 8, 10 and 12 for an unrepaired soil sample was 5.63E-05, 3.04E-05, 3.00E-05, 3.07E-05, 2.94E-05 and 2.99E-05, respectively; the total carcinogenic risk of Cd in the repaired soil is as follows in sequence: 1.99E-07, 2.03E-07, 2.42E-07, 2.49E-07, 2.62E-07 and 2.72E-07; namely, the total carcinogenic risk of Cd in the unrepaired soil sample is well reduced by the high-temperature curing treatment technology, so that the soil sample with the heavy metal human health risk is converted into the soil sample without the heavy metal human health risk; the method effectively avoids the possibility of underestimating the heavy metal hazard index and/or the total carcinogenic risk of the repaired soil under neutral and alkaline conditions, and also avoids the possibility of underestimating the total carcinogenic riskThe possibility of overestimating the heavy metal hazard index and/or the total carcinogenic risk of the unrepaired soil under neutral and alkaline conditions realizes quantitative and accurate evaluation of the human health risk of the soil after heavy metal restoration in the recycling process.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. A method for evaluating human health risks of heavy metal contaminated soil is characterized by comprising the following steps:
(1) respectively leaching heavy metals in the soil sample in leaching agents with different pH values, and measuring the leaching concentration C1 of the heavy metals in the soil sample under the leaching agents with different pH values to obtain a functional relation C1(pH) between the leaching concentration of the heavy metals in the soil sample and the pH value of the leaching agent;
(2) measuring the acid soluble state concentration C2 of the heavy metal in the soil sample leached in the step (1), and constructing a functional relation C2(pH) between the acid soluble state concentration of the heavy metal in the soil sample and the pH value of the leaching agent;
(3) calculating human health risk concentration C in soil samplerisk: wherein, Crisk＝0.5×C1(pH)+0.5×C2(pH)；
(4) Calculating the total carcinogenic risk and/or hazard index of the heavy metals in the soil sample;
(5) and evaluating whether the human health risk of the heavy metal contaminated soil exists or not.
2. The method for assessing the human health risk of heavy metal contaminated soil according to claim 1, wherein:
the leaching time in the step (1) is more than or equal to 7 days.
3. The method for assessing the human health risk of heavy metal contaminated soil according to claim 1, wherein:
the pH gradient of the leaching agent in the step (1) is more than or equal to 5;
the pH value range of the leaching agent is 2-12;
the leaching agent comprises at least two alkaline leaching agents and at least two acidic leaching agents.
4. The method for assessing the human health risk of heavy metal contaminated soil according to claim 1, wherein:
the mass volume ratio of the soil sample to the leaching agent in the step (1) is 1 (15-25).
5. The method for assessing the human health risk of heavy metal contaminated soil according to claim 1, wherein:
the method for measuring the acid dissolution state concentration of the heavy metal in the step (2) is as follows: and (2) mixing the soil sample leached in the step (1) with acid, oscillating, and measuring the acid dissolution state concentration of the heavy metal.
6. The method for assessing the human health risk of heavy metal contaminated soil according to claim 1, wherein:
and (4) referring to relevant parameters and calculation models provided in technical guidelines for evaluating risks of soil pollution of construction sites (HJ25.3-2019) in the method for calculating the total carcinogenic risks and/or the hazard indexes in the step (4).
7. The method for assessing the human health risk of heavy metal contaminated soil according to claim 1, wherein:
the total carcinogenic risk in the step (4) is the sum of the carcinogenic risk of oral intake, the carcinogenic risk of percutaneous intake and the carcinogenic risk of intake of surface particulate matter by inhalation;
the hazard index in the step (4) is the sum of the hazard quotient of oral intake, the hazard quotient of skin intake and the hazard quotient of intake of surface particulate matter by inhalation.
8. The method for assessing the human health risk of heavy metal contaminated soil according to any one of claims 1 to 7, wherein:
the evaluation method in the step (5) refers to the evaluation criteria provided in technical guidelines for evaluating the risk of soil pollution in construction sites (HJ 25.3-2019).
9. The method for assessing the human health risk of heavy metal contaminated soil according to any one of claims 1 to 7, wherein:
the soil sample is a repaired soil sample;
the heavy metal is preferably at least one of copper, zinc, lead, cadmium, nickel and chromium.
10. The application of the method for assessing the human health risk of the heavy metal contaminated soil according to any one of claims 1 to 9 in the field of environmental detection.
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